316L Swing Check Valve H44W

Check Valve — Full Professional English Translation

Working Principle

Check valves allow medium to flow in only one direction and automatically prevent reverse flow. They operate automatically: when forward fluid pressure lifts the disc open; upon flow reversal, fluid pressure plus the disc’s own weight presses it tightly against the seat to shut off the pipeline.

Typical examples include threaded check valves and wafer check valves. The two main classifications are swing check valves and lift check valves:

1. Swing Check Valve

Equipped with a hinge mechanism, the disc swings freely like a door against the inclined seat surface. The hinge design ensures the disc can fully open and achieve complete, reliable sealing each time it closes. Disc bodies can be all-metal, or lined with leather, rubber, or composite overlay, depending on application demands. When fully open, fluid resistance is extremely low with minimal pressure loss.

2. Lift Check Valve

The disc sits on the sealing surface of the valve body. Upstream pressure lifts the disc to allow passage; once flow reverses, the disc falls back onto the seat to block backflow. Available in all-metal construction or with resilient sealing faces. Compared to swing type, lift check valves feature a narrower flow path, higher pressure drop, and limited flow capacity.

 Installation Types

1. Swing Check Valve

Disc is disc-shaped, rotating on a pin outside the valve seat. Internal channel is streamlined, with lower flow resistance than lift check valves. Suitable for large diameter pipelines with steady low velocity flow; not ideal for pulsating service or ultra-high tightness requirements. Available in single-disc, double-disc & multi-disc designs, installed to prevent backflow and reduce water hammer damage.

2. Lift Check Valve

Disc slides vertically along the valve centerline. Threaded end models can only be mounted horizontally; wafer type can be installed on both horizontal and vertical runs. Shares similar structure with globe valves, resulting in higher fluid resistance. When medium flows forward, pressure lifts the disc; on reverse flow, the disc reseats by its own weight. Outlet direction is perpendicular to pipeline for lift type, and parallel for swing type, with slightly higher flow resistance.

3. Butterfly Check Valve

Rotates on a central spindle. Simple construction, can only be installed horizontally, with excellent sealing performance.

4. Wafer Lift Check Valve

Moves along the valve central axis. As an innovative new design, it features compact size, light weight, excellent manufacturability, and is a major developing trend for check valves. Its flow resistance is slightly higher than swing check valves.

5. Pressure Seal Check Valve

Specially designed for boiler feedwater and steam turbine cut-off service. Combines the advantages of both lift check valves and globe/angle valves.

Additionally, there are special designs unsuitable for pump outlet installation, including foot valves, spring check valves, Y-type check valves, etc.